1. Field of the Invention
The invention relates to a method and device for supporting calls such as IMS emergency calls from a subscriber terminal having no subscriber identity module (UICC-less in I-WLAN access network.
2. Description of the Related Art
The growth of public WLANs provides an opportunity for appropriately-equipped terminal devices (or user equipments (UE) in 3rd generation terminology) to access cellular home networks and visited networks via such WLANs. WLANs which provide such an interworking functionality are therefore referred to as I-WLANs. The I-WLANs are connected to public land mobile networks (PLMNs) enabling UEs to access network services on home networks (HPLMNs) and visited networks (VPLMNs).
Wireless devices will be bound by law to support emergency calls. Reporting of an emergency should be possible even when no session is currently active over a particular radio channel of a multi access device, i.e. the user is presently not attached to any radio, or a subscriber identity module (SIM) or universal mobile telecommunications system SIM (USIM) is presently not inserted in the device.
Usually, emergency reports initiated by pulling a switch or calling an emergency number are generally treated in a prioritized manner, so that access is readily available to invoke the emergency alarm. However, wireless devices may not have reliable functions or be used reliably during an emergency, so that entering of passwords or other authentication processes may not be done correctly. Moreover, a wireless device may be near a network or access network but not associated to that network. Therefore authorization is not needed before the alarm is sounded or contact is made to the emergency center in order to expedite the Emergency call.
I-WLAN (interactive wireless local area network) access is defined in specifications TS 23.234, 33.234, 24.234 and 29.234 of the 3rd generation partnership project (3GPP). For direct IP access (so-called Scenario 2) and 3GPP IP access (so-called Scenario 3), an Extensible Authentication Protocol (EAP) SIM/AKA (Authentication and Key Agreement) procedure is used for authentication, wherein authorization is done based on a subscriber check against information held at a subscriber database, e.g., a home subscriber server (HSS).
The W-APN Network Identifier for the support of IMS Emergency calls shall take the form of a common, reserved Network Identifier of the form “sos”, e.g. “sos.w-apn.mnc012.mcc345.pub.3gppnetwork.org”, as defined in TS23.003.
This kind of W-APN indicates to a WLAN access network or to a 3GPP AAA Server that access is needed for an emergency call or another prioritized call.
At present, there is no agreed solution in 3GPP yet for which kind of authentication method and user ID will be used for UICC-less users (users without a universal integrated circuit card) to access I-WLAN for IMS emergency.
It is possible to use a common user name and common password for all users in I-WLAN for UICC-less IMS emergency call.
In temporary document S2-051950 of 3GPP TSG SA WG2 Architecture, 5-9 Sep. 2005, a Voice over Internet Protocol (VoIP) emergency call support is described, where VoIP emergency calls are supported via a WLAN by using a pseudo IMSI (International Mobile Subscriber Identity) to facilitate WLAN access. The pseudo IMSI can then be used to create a user-specific pseudo network access identifier (NAI) to be used for initial access and the authentication procedure. The pseudo IMSI is made up of a unique combination of mobile country code (MCC) and mobile network code (MNC) and digits from the international mobile equipment identity (IMEI). VPLMNs advertised by the WLAN could either all be capable of supporting authentication using the pseudo NAI for emergency services or might be presented to a UE in a prioritized order indicating capability and willingness to support this. The VPLMN would then treat the UE as a temporary home subscriber and either skip authentication and authorization (AAA) or ensure that it succeeds.
However, also in this case, the session can not be continued.
In current TS 23.234, the requirement for support IMS emergency calls is to provide WLAN UEs with IP bearer capability to access IMS Emergency calls for both UICC and UICC-less cases. Moreover, authentication may be (i) skipped entirely or (ii) use a dummy or null authentication method.
Thus, currently, no reliable mechanism is specified for UICC-less user's IMS Emergency calls over I-WALN. And there is no definition of the user ID to be used for UICC-less user, which is needed to form the NAI (together with the W-APN).